Solid state lighting (“SSL”) devices generally use solid state emitters (“SSEs”) such as semiconductor light-emitting diodes (“LEDs”), organic light-emitting diodes (“OLEDs”), and/or polymer light-emitting diodes (“PLEDs”) as sources of illumination rather than electrical filaments, plasma, or gas. A conventional type of SSL device has a “white light” SSE. White light requires a mixture of wavelengths to be perceived by human eyes. However, SSEs typically only emit light at one particular wavelength (e.g., blue light), so SSEs are modified to generate white light. One conventional technique for modulating the light from SSEs includes depositing a converter material (e.g., phosphor) on the SSE. For example, FIG. 1 shows a conventional SSL device 10 that includes a support 2, an SSE 4 attached to the support 2, and a converter material 6 on the SSE 4. The SSE 4 emits light (e.g., blue light) radially outward along a plurality of first vectors 8. The converter material 6 scatters some of the light emitted by the SSE 4 and absorbs other light emitted by the SSE 4. The absorbed light causes the converter material 6 to emit light of a different color along a plurality of second vectors 12. The light from the converter material along the second vectors 12 can have a desired frequency (e.g., yellow light) such that the combination of light along the first and second vectors 8 and 12 appears white to human eyes if the wavelengths and amplitudes of the emissions are matched appropriately.
One challenge associated with conventional SSL devices (e.g., the SSL device 10 shown in FIG. 1) is that the color of light generally varies across the SSL devices due to the emission angle. As shown in FIG. 1, when the SSE 4 is treated as a point source, the emission angle θ is the angle that light (e.g., along the first vectors 8) projects away from an axis N normal to the support 2. The distance light travels through the converter material 6 accordingly changes as a function of the emission angle θ. As shown in FIG. 1, for example, the first vectors 8 having greater emission angles θ (e.g., 60°) travel greater distances through the converter material 6 than the first vectors 8 having smaller emission angles θ (e.g., 10°). The longer a first vector 8 travels through the converter material 6, the more light from the SSE 4 the converter material 6 absorbs, and the more light the converter material 6 generates. As a result, light with a large emission angle θ and thereby a longer path through the converter material 6 includes less blue light from the SSE 4 and generates more yellow light from the converter material 6. Conversely, light with a small emission angle θ and thereby a shorter path through the converter material 6 includes more blue light from the SSE 4 and generates less yellow light from the converter material 6. Therefore, when viewed head-on, the color of light emitted by the SSL device 10 may appear more bluish, and when viewed from the side, the color of light may appear more yellowish. Accordingly, the emission angle θ of the light can result in color variance across the viewing angle of the SSL device 10.